[…] in 1876, a nurseryman imported some Japanese chestnut seeds that carried a fungus to which the American chestnut had no resistance. The blight was discovered in 1904 at the Bronx Zoo, a few hundred yards from where this scraggly young tree now stands, and it spread with shocking speed. By 1950, four billion American chestnuts—99.9 percent of the species—had died, their bark ripped open to reveal a sickly orange rot girdling their trunks.
This little tree in front of me was different. I leaned in close and put my hands against it. There were half a dozen cankers up and down its trunk, but wherever the smooth gray bark had split, it had then scabbed over, black and warty. The wounds looked contained. It was engaged in a battle with the blight, but it was neither winning nor losing that battle.
The sign at the base of the tree read “American Chestnut Trial, Castanea dentata, Darling 4.” What it didn’t indicate was that this tree and two other chestnuts growing nearby were the only genetically modified organisms (GMOs) in the New York Botanical Garden. Born in a lab in Syracuse, Darling 4 was engineered by geneticists who inserted a wheat gene into a wild chestnut embryo extracted from an immature nut. The gene gives the chestnut the ability to make an enzyme that detoxifies the blight—a skill none of the four billion American chestnuts that preceded it ever developed.
GMOs on balance are GOOD, even the corn etc, since ultimately for any health concerns there may be about Roundup (which are still unproven at this point), the overall environmental impact of farming this way is still lower than with alternative methods that can be utilized. We can grow more crops using less land and resources, and they don’t have to use even harsher chemicals in lieu of glyphosate. This point is not the same as endorsing Bayer/Monsanto as a company.
With regards to the chestnut, I feel like this falls into the category of “we effed it up, we need to fix it”. And if this is the way to do it, let’s run with that.
I do worry about the genetic diversity, and I’m wondering if part of the plan is to crossbreed these resistant clones with each other, as well as the 15/16 American/Chinese hybrids the ACF is working on, to breed in not only genetic diversity, but multiple lines of resistance. I also wonder how the trait is passed on to offspring.
I would agree that this should be of the paramount concern with this blight-resistant chestnut. The risk is to spend a whole bunch of money planting out these trees, only for resistance to be breached in 25 or 30 years.
If the wheat gene is a single trait type resistance to the blight fungus then it is very likely to be breached by the fungus at some point in the future. I believe races of apple scab have breached the Vf mechanism of scab resistance in both Europe and North America.
The question is, how do you test that? Essentially the way it was tested in apples was lots of chances - planting lots of Vf-trait carrying apples and flowering crabs and exposing them in the wild to lots of scab spores. Eventually the genetic dice roll produces a fungus with a trait that breaches the resistance and its done. As long as the trait doesn’t significantly weaken the fungus the resistance is gone. Natural selection at its heart.
Actually I encountered a chestnut (evidently the native American) about 5 inches in diameter and 50 feet or so tall. In city of Berea KY. Was asked into a backyard to look at dogwood and other trees not doing well. And saw this small prickly husk from a chestnut…much smaller than the Chinese or hybrids I see normally in people’s yards. Spotted the culprit…I mean the tree responsible for the hull…several feet across a high fence in a neighbor’s yard.
I haven’t pursued it…too many other irons in the fire.
I’ve seen regrowth from stumps over the years…as I was raised where I could roam over 350 acres, about 90 percent woodlands…with many old dead chestnut logs rotting.
I recall logs lying on the ground too big to cross over as a child.
Some forms of resistance are inherently durable. Oxalic acid oxidase is one example because it deactivates a primary biopath for virulence in the blight arsenal. If you read the article carefully, the modified tree is resistant, but it still produces cankers. Cankers are not good for producing wood. Combining the OaO gene with other sources of resistance is expected to reduce the size and number of cankers.
There are problems with the current OaO modified trees. They produce the chemical in all tissues. A current target of ACF is to modify an American Chestnut with the gene and including a promoter that is only triggered by wounding. In other words, a tree that would produce Oxalic Acid Oxidase as a response to wounding, not in all tissues.
If you want to read about another inherently durable fungicide, check out Strobilurin. It is produced by a group of mushrooms to prevent other fungi from encroaching on their territory. Strobilurin attacks a critical biopath in most fungi. Only other strobilurin producing mushrooms are tolerant. It is extremely unlikely that other fungi will overcome the effect of strobilurin. Treatment programs are still structured to use other fungicides to avoid over-reliance on a single chemical.
I planted 6 Dunstan this year. I got them in Alachua Florida. These guys seem to be fighting the good fight. Mine are only 3 year old trees and only in my ground for less than 6 months but seem to love it here. This is the company. http://www.chestnuthilltreefarm.com/store/c/31-Dunstan-Chestnut-Trees.aspx
I bought 6 persimmon as well and they are doing nicely as well.
I read up months ago on this forum about the devastating loss of chestnuts and not only wanted to help bring them back but see that they are really great trees for wildlife. Seems deer love the nuts…
They’re not American though. They’re probably about 90% Chinese. Most Chinese chestnuts have a high degree of blight resistance. If you want good quality eating nuts there are much better trees to plant than the Dunstan seedlings.
Unless you are planting acres of trees, I would suggest buying grafted Dunstons for growing in Florida, which is where they were bred- and specifically for nut quality. If you want to save money, the seedlings should also have most of the positive traits of the clones. They aren’t all that expensive, but you can sprout your own nuts if you want something cheap.
There’s an objective article on Dunston chestnuts in this.
It’s rare but some do survive to that size… Before they succumb. The longer side of the loop trail to Crabtree Falls in North Carolina, along the Blue Ridge Parkway. There are lots of seedlings and suckers from stumps of long gone mature trees. One I noticed was similar, probably 5" diameter and at least 50’ tall.
What it would be like to go back in time and roam the mountains where they reigned.
You cannot buy grafted Dunstan cultivars from Chestnut Hill because they don’t sell them anymore. Too many graft failures. The Dunstan trees were never bred for nut quality. They were bred for blight resistance. They are all descended from the three Chinese cultivars Meiling, Kuling and Nanking, none of which are known for their nut quality. The resultant Dunstan cultivars generally have average nut quality at best, although Revival is quite good and Carpenter has a decent sweet nut. At one time I had all of the Dunstan cultivars except Heritage. The only one I have kept is Revival but it will probably eventually die because of delayed graft union failure. The random seedlings that are now sold by Chestnut Hill generally produce very average nuts which is what you would expect. There are many cultivars available in the US that produce much better quality seedlings than the Dunstan trees. The chestnut breeding program being conducted by Dr Greg Miller of Empire Chestnut Company in Ohio, that formally began in 2017 includes growers from across the eastern US, does not use any Dunstan trees. Some of teh best trees used in that program originated in Alabama and Georgia. The fact that the Dunstan trees are grown in Florida is not important. Chinese chestnuts are widely grown in China in humid condition in zones 7-9. They are already acclimated to southeastern US growing conditions.
Here’s a photo of nuts from the Missouri cultivar “Black Satin”. The nuts are larger than any of the Dunstan nuts and the nut quality is superior as well. This is a seedling of Greg Miller’s cultivar “Peach.”
Here’s a photo of nuts from the cultivar “Kyoung”, that originated in Tennessee. The nuts are about the same size as the larger Dunstan nuts and the nut quality is also superior. Seedlings from Kyoung are known for being very vigorous.
Here’s a photo of nuts from the cultivar “Jenny”. The nuts are larger than any of the Dunstan nuts and the nut quality is also superior. The nuts also drop earlier in the season than any of the Dunstans.
I stand corrected except for one part. Dunston’s son claims to have bred them for nut quality as much as for blight resistance.
However, your experience dwarf’s mine, although my one grafted Dunston has sweet but smallish nuts. I have Sleeping Giant and a couple of others from Nolan, I believe, that do produce bigger, sweeter nuts, but, so far, not at adequate levels of production even though they’ve been bearing for a decade.
Do you know any nurseries that sell “Jenny”. I WANT that.
Max Draughn has a large planting of Dunstan seedlings that produce heavily each year. I would rate nut size as small on average. I did not see blight in the trees though I did not specifically look for it as we were there to look at pecans. There is a possibility the trees could be carefully culled to find one or two that are worth propagating. Otherwise, they are just a good source of deer feed.
By breeding for quality I think he means that he picked out the best quality nuts he could find on the trees he had. I know he did that because Bob and I have sat in the Dunstan orchard in Alachua tasting nuts and talking about it. But that was never the primary objective (which was finding blight resistant timber type trees) and they took no steps to broaden their gene pool, which was never optimal for nut quality (their nuts also have a lot of double embryos). I think they relied a lot on the fact that Revival, their flagship tree, had a good quality nut. The drop-off from Revival however was significant and unfortunately many Revival trees had delayed graft union failures. At this point I think their seedlings have become somewhat inbred. They should probably bring in some new genetics but that would take time and money and they are already selling huge amounts of trees at premium prices so they probably don’t see a need to improve the nut quality, again because that is not their primary objective. A lot of deer hunters are satisfied with the Dunstan seedlings and the deer aren’t picky about the taste, so everyone is happy, except for those buyers who thought they were getting top of the line eating nuts.
Washington Chestnut Company is trying to ramp up to sell Jenny trees. Forrest Keeling Nursery should have it at some point in the future. Empire Chestnuts has Jenny also but they are not selling grafted trees any more. Jenny seedlings also tend to be very vigorous so some people are just planting Jenny nuts.
Do you have any suggestions for varieties that might produce here in Reno? I’ve tried a couple of times to grow chestnuts (seedling Americans, because I figured that blight would be unlikely here) but they all failed, mostly, I think, due to the cold, dry winter conditions here.
I’m sure I can grow chestnuts if I give them a bit more TLC their first couple of winters. I’ll need earlier ripening varieties. Taste is always important to me, but actually getting ripe nuts is priority #1.
Winter is not your problem. It gets far colder in the northeastern US than it does in Reno. Your problem is your alkaline soil. Almost all of the Reno area has a soil pH of 7.0 or above. Chestnuts need acidic soil below 6.9. American chestnuts particularly need more acidic soils down below 6.5. Some European trees will do OK from 6.5-7.0. but American trees are not as tough as the European trees. If you can find soils in the 6.5 - 7.0 range you may be able to grow some European trees. There are very few areas in the Reno-Carson City area that have acidic soils. There may be some near rivers or creeks and I know there are some acidic soils as you climb the mountains toward Lake Tahoe, but generally most soils are alkaline.
Thank you for the prompt, informative answer. I’ll do soil tests in the areas I would want trees. I think I’m likely to strike out here. My property backs up to two seasonal drainages, but I doubt that has resulted in much of an increase in acidity.
